Human sociability depends fundamentally on our ability to communicate and comprehend non-verbal affective information. It is easy to appreciate the importance of facial expression to the human experience by simply observing an infant's rapid response to a smiling parent. The goals of the first study proposed are the following: (1) to document developmental change in facial affect discrimination beginning at the age of 4 years old; and (2) utilizing functional magnetic resonance imaging (fMRI), the relationship between developmental changes in the neural architecture underlying facial affect discrimination and developmental change in the ability to discriminate facial affect will be delineated. Taken together these studies will provide critical information regarding normal developmental change in the neural and cognitive/perceptual systems devoted to processing affective information. The final study proposed will utilize fMRI to understand developmental change in a fundamental form of nervous system plasticity, i.e. habituation. Attenuation of brain activity following repeated exposure of a stimulus, the signature of habituation, in the neural systems mediating affective experience may be an important indicator of the fidelity of the human affective processing system. These studies have broad implications for our understanding of childhood onset psychiatric disorders, and certain neurodevelopmental disorders, e.g. autism, which grossly impair social and affective behaviors. [unreadable] [unreadable]